Method of controlling fuel supply to internal combustion engine

ABSTRACT

The calculation of an adjustment value, which is determined by the concentration of oxygen in the exhaust gas, the opening of a throttle valve provided in an intake air passage to the engine, the engine temperature, etc., is started every time a predetermined number of repeatedly produced start signals, the repetition rate of which corresponds to the rotational speed of the crankshaft, occur. A basic value for fuel supply, T p  =k Q/N, is calculated from the engine operating parameters; the amount of flow of intake air into the engine, Q the rotational speed of the crankshaft, N, and a constant k, and adjusted according to the adjustment value to obtain a control output signal, in the vicinity of the next start signal after said predetermined number.

BACKGROUND OF THE INVENTION

The present invention relates to a method of controlling fuel supply toan internal combustion engine, and more particularly relates to a methodof controlling fuel supply to an internal combustion engine comprisingthe steps of calculating a basic value for fuel supply to the enginefrom fundamental operational parameters of the engine, calculating anadjustment value for this basic value, and adjusting the basic valueaccording to the adjustment value to obtain a final control outputvalue.

In FIG. 1 of the accompanying drawings is shown a timing chart forcalculation of a final control output value which, in this case, is avalue representing the amount of fuel injection for an internalcombustion engine. The amount of fuel injection is determined bycalculating a basic value for fuel supply, T_(p) =k Q/N, fromfundamental operational parameters of the engine; the amount of flow ofintake air, Q, into the engine, a constant k and the rotational speed ofthe crankshaft, N, and adjusting the basic value according to anadjustment value which depends on the output of an oxygen sensor, notshown, which senses the concentration of oxygen in the exhaust gas; theopening of a throttle valve, not shown, provided in an intake airpassage to the engine; and the temperature of the engine. Thus, fuel issupplied to the engine according to the final control output value oncefor each rotation of the crankshaft. In FIG. 1, it is assumed that theengine is a 6-cylinder type engine. A crank angle signal 10 is shown asconsisting of pulses of R₁, R₂, R₃, R₄ . . . , which are sequentiallyproduced at crankshaft rotational intervals of 120°. The adjustmentvalue is calculated once for each rotation of the crankshaft, at timeperiods A₁ and A₂. A calculation start signal 12 is shown as being aclock pulse signal containing clock pulses T₁ . . . T₁₁, but couldalternatively be a signal synchronized with the crank angle signal.Calculation of the basic output data, shown by 13, is started, for eachof the time period shown as B₁, B₂, . . . B₁₁, when each of the pulsesT₁, T₂ . . . of the calculation start signal 12 is received. A fuelinjection valve drive signal 14 is shown as consisting of pulses C₁, C₂,one being produced for each rotation of the crankshaft. The latestcompleted basic output data obtained at time periods B₁ and B₉ are usedfor control of fuel supply, after correction by the latest adjustmentvalue. Thus the latest adjustment value obtained at A₁ is used forcorrecting the output value at B₉.

As shown in FIG. 1, to simplify the structure of the control deviceused, the timing of R₁ and the start of A₁ and C₁ are selected to be thesame, and the timing of R₄ and the start of A₂ and C₂ are selected to bethe same.

The problem with the above described method according to the timingchart shown in FIG. 1 is that the adjustment value obtained at A₁ iscalculated one full crankshaft rotation before C₂, and this value isused for adjusting the basic output value which defines fuel injectiontime C₂, in the time period B₉ starting from pulse T₉. Thus theadjustment value is rather old, compared with the basic value which itis used to correct. During operation of the engine at substantiallyconstant load and at substantially constant speed, no large effect dueto this will occur on the operation of the engine, whereas, however,during a time when the operating conditions are fluctuating, it isdifficult to maintain the air/fuel ratio at a proper constant value whenthe amount of fuel supplied to the engine is controlled on a feedbackbasis, for example, using information on the components of the exhaustgas.

SUMMARY OF THE INVENTION

Therefore, it is an object of the invention to provide a method ofcontrolling fuel supply to an internal combustion engine, which avoidsthe above explained problems.

According to the present invention, there is provided a method ofcontrolling fuel supply to an internal combustion engine having acrankshaft, comprising the steps of; starting to calculate an adjustmentvalue every time a predetermined number of repeatedly produced startsignals, the repetition rate of which corresponds to the rotationalspeed of the crankshaft, occur; calculating a basic value for fuelsupply from engine operating parameters, and adjusting the basic valueaccording to the adjustment value to obtain a control output signal inthe vicinity of the next start signal after said predetermined number ofstart signals.

Thus, according to the present invention, the basic value is adjustedaccording to a more recent adjustment value, thereby improving control.When the operating conditions, such as the load, change rapidly, propercontrol is possible of the flow of fuel in a feedback mode, using thesensed ratio of exhaust gas components, for example. This brings about astable mixture ratio of air and fuel.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages will be apparent from the followingdescription, taken in conjunction with the accompanying drawings whichare given by way of illustration only and which is not intended to belimitative. In the drawings:

FIG. 1 is a timing chart of a method of controlling fuel supply to aninternal combustion engine;

FIG. 2 is a similar timing chart of a method according to a firstembodiment of the present invention;

FIG. 3 shows in detail the step of preparing a final output controlvalue in the method of FIG. 2;

FIG. 4 is a flowchart of a program which executes the method of FIG. 2;

FIG. 5 is a flowchart of a program which calculates adjustment value inthe method of FIG. 2;

FIG. 6 is a timing chart of a second embodiment of the method of thepresent invention;

FIG. 7 shows in detail the step of preparing a final output controlvalue in the method of FIG. 6; and

FIG. 8 is a flowchart of a program which executes the method of FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 2 is shown a timing chart for carrying out, by a computerprogram, a first preferred embodiment of the method according to thepresent invention. In order to contrast the method according to thepresent invention and the method illustrated in FIG. 1, the samereference numeral denotes corresponding signals or signal components,and calculation of an amount of flow of fuel supplied to a 6-cylinderinternal combustion engine is shown as an example only. Since the engineis a 6-cylinder engine, the crank angle signal 10 consists of a train ofpulses R₁ to R₅, etc., produced sequentially at crankshaft rotationalintervals of 120°. The calculation start signal 12 is a clock pulsesignal consisting of pulses T₁ to T₁₂ which are produced independentlyof the crank angle signal.

In order to produce the fuel injection valve drive signal 14, shown asconsisting of pulses C₁, C₂, etc., for every three pulses of the crankangle signal 10, a ternary counter, not shown, is used to process thepulses of the crank angle signal 10. The contents of the count in thecounter can be classified as being 3n, 3n+1, or 3n+2, where n=0, 1, 2, .. . N. According to the program, the adjustment value is calculated atevery count value 3n. Calculation of the final output value is effectedbefore every (3n+1), and the injection valve is driven at every countvalue (3n+1). A state signal consisting of two bits can be used,changing as "00", "01", "11", "00". . . , to calculate the adjustmentvalue at "00" and to produce the injection value drive signal 14 at thestate of "01".

As shown in FIG. 2, the calculation of the adjustment value is startedat R₁ and carried out for a time period of A₁. The adjustment value thusobtained is used for adjustment of basic output value calculated in eachtime period B₃ to B₁₀. Thus, since the final control output value usedfor the fuel injection for the time period represented by C₁ is thelatest value calculated at B₄, the latest adjustment value obtained atA₁ is used. In the same way, the final control output value used for thefuel injection for the time period shown by C₂ is adjusted at B₁₁according to the adjustment value obtained at A₂.

Referring to FIG. 3, the details of calculation of the output value ineach time period B are shown. The program makes the time point 20 ofcompleting A/D conversion of the amount of flow of intake air coincidentwith the pulse of the calculation start signal 12 (clock pulse signal).When the calculation of the amount of flow of intake air, shown by 21,is completed, a basic value for fuel injection is calculated at 22,using data such as the rotational speed of the crankshaft, the amount offlow of intake air, etc., (the rotational speed of the crankshaft isbeforehand calculated separately). Simultaneously with the completion ofthe calculation of the basic value, shown at 22, the adjustment value istaken in at time point 23, and, when the calculation of the finalcontrol output value at 24, (correcting the basic value using theadjustment value) is completed, the final output control value is sentto an output interface, not shown, at time point 25 for output. As shownin FIG. 3, since the basic value for fuel injection is calculated at 22immediately after the amount of flow of intake air is determined, thisbasic value calculation is effected using the latest availableinformation.

When both calculations, shown by A and B, overlap, it is arranged suchthat one of them is of first priority, or alternatively the one whichhas been earlier carried out is of first priority. In FIG. 2, A₁, B₂,etc., are shown as overlapping, for the purpose of clarifying thedescription.

The output interface to which the final output control value, the,calculation of which is shown in FIG. 3, is fed is updated by the latestvalue thereof, and supplies an output when each of the pulses R₂ and R₅is input thereto.

In FIG. 4 the steps of calculation shown in FIG. 3 are shown as aflowchart. When the A/D conversion of the amount of flow of intake airis completed, an interrupt request is effected at 26, so that the seriesof calculations of the amount of intake air, shown by 27, the basicvalue, shown by 28, and correction of the basic value using theadjustment value, shown by 29, are carried out.

In FIG. 5 is shown a flowchart for starting a program to calculate theadjustment value. In the particular example shown in FIG. 2, the crankangle signal 10 includes pulses R₁ to R₅ sequentially produced atintervals of 120°. Interrupt requests R₁ to R₅ occurring sequentially atintervals of 120°, shown at 31, start a ternary counter, not shown, at astep 32 of the program. If the counted number of pulses of the crankangle signal is 3n, where n=0, 1, 2 . . . n, calculation of theadjustment value starts at 33. If the counted number of pulses at thecrank angle signal is 3n+1, the contents of the ternary counter is 1, sothat the fuel injection valve drive signal 14 occurs, as C₁ and C₂defining fuel injection time periods, respectively. The adjustmentvalue, obtained at 33 in FIG. 5, is used in the output calculation at 29in FIG. 4.

In FIG. 6 there is shown a timing chart of a second embodiment of themethod of the present invention, also carried out by a computer, inwhich the calculation start signal 12 is given by pulses R₁ to R₅ of thecrank angle signal 40, occurring at intervals of 120°, without using anyclock pulse signal such as shown in FIGS. 1 and 2. The calculation ofthe adjustment value, shown by 41, is shown as being carried out at thetime periods A₁ and A₂. The calculation of the output value is shown asbeing carried out at the time periods B₁ and B₂. The fuel injectionvalve drive signal 43 is shown as containing pulses C₁ and C₂ definingfuel injection time periods, respectively. As shown in the figure, theadjustment value is calculated for the time periods A₁ and A₂ whichstart with the signal pulses R₁ and R₄ produced sequentially at crankrotational intervals of 360°. The output value is calculated for thetime periods of B₁ and B₂ starting with R₂ and R₅, respectively.Immediately after this calculation, the fuel injection valve is drivenat C₁ and C₂.

In FIG. 7 are shown the details of calculating the output data duringtime periods B₁, B₂ shown in FIG. 6. The A/D conversion of the amount offlow of intake air is started at 45, which is simultaneous with thepulses R₂ and R₅ of the crank angle signal. Immediately after thisconversion at 45, an amount of flow of intake air is calculated at 46,and a basic value for fuel injection is calculated at 47 from data suchas the rotational speed of the crankshaft, the amount of flow of intakeair, etc. The adjustment value calculated at A₁ , or A₂ is taken in attime point 48, and then the basic value is adjusted at 49 according tothe adjustment value to obtain a final output value. Immediately afterthis adjustment, each of the pulses C₁, C₂ of the fuel injection drivesignal 43 starts fuel injection at 50. In this particular embodiment,the number of repetitions of calculating the basic value is relativelysmall, and it is therefore possible for the computer to perform othercontrol functions between the pulses R₃ and R₄.

FIG. 8 shows a flowchart of a program which corresponds to the timingchart of FIG. 6. Each time the pulses R₁ to R₄ of the crank angle signalare produced sequentially at an interval of 120°, an interrupt requestto the computer is effected at 51. This interrupt request signal is sentto a ternary counter, not shown, which classifies the number ofinterrupt requests produced, at 52, with respect to 3. When the numberis 3n, the adjustment value is calculated, at A, i.e. at a step 53. Whenthe number is 3n+1, the calculation of the output value at B is effectedat 54. When the number is 3n+2, calculations other than the calculationfor fuel injection can be performed at 55. The final output controlvalue is fed at 56 to a memory, not shown. The final control value fedfrom block 54 to the memory is immediately used for fuel injections atC₁ or C₂.

While the present invention has been particularly shown and describedwith reference to preferred embodiments thereof, it will be understoodby those skilled in the art that the foregoing and other changes in formand details may be made therein without departing from the spirit andscope of the present invention.

What is claimed is:
 1. A method of controlling fuel supply to amulticylinder internal combustion engine having a fuel injection valveand a plurality of sensors for measuring engine operating conditions,comprising the steps of:(a) measuring engine crankshaft rotation; (b)producing a crank angle pulse signal on the basis of said crank rotationmeasurement, the pulses of which signal occur each time the crankshaftrotates through a predetermined angle; (c) measuring a plurality ofother engine operating conditions; (d) producing information signalsindicative of the plurality of the other engine operating conditions;(e) beginning a calculation of a fuel injection duration adjustment andcalculating the adjustment as a function of at least one informationsignal indicative of engine operating conditions in response to a firstpulse of said crank angle signal; (f) starting a calculation of a basicfuel injection duration and calculating the duration as a function ofinformation signals indicative of engine operating conditions, includingcrankshaft rotation, after the fuel injection duration adjustmentcalculation, ending the basic fuel injection duration calculation beforethe crank angle signal pulse immediately following said first pulse; (g)starting a calculation of an output value and calculating the value as afunction of said basic fuel injection duration and said fuel injectionduration adjustment after said basic fuel injection durationcalculation, ending the output value calculation before the crank anglesignal pulse immediately following said first pulse; (h) opening thefuel injection valve in response to the crank angle signal pulseimmediately following said first pulse; and (i) closing the fuelinjection valve after a time interval corresponding to said outputvalue.
 2. A method of controlling fuel supply to an internal combustionengine having a fuel injection valve and a plurality of sensors formeasuring engine operating conditions, comprising the steps of:(a)measuring engine crankshaft rotation; (b) producing a crank angle pulsesignal on the basis of said crank rotation measurement, the pulses ofwhich signal occur for each crank rotation of 720°/P, where P is thenumber of engine cylinders; (c) measuring a plurality of other engineoperating conditions; (d) producing information signals indicative ofthe plurality of other engine operating conditions; (e) beginning acalculation of a fuel injection duration adjustment and calculating theadjustment as a function of at least one information signal indicativeof engine operating conditions in response to a first pulse of saidcrank angle signal; (f) starting a calculation of a basic fuel injectionduration and calculating the duration as a function of informationsignals indicative of engine operating conditions, including crankshaftrotation, in response to the crank angle signal pulse immediatelyfollowing said first pulse; (g) starting a calculation of an outputvalue and calculating the value as a function of said basic fuelinjection duration and said fuel injection duration adjustmentimmediately after said basic fuel injection duration calculation; (h)opening the fuel injection valve immediately after said output valuecalculation; and (i) providing a control signal representative of saidoutput value, and displacing said control signal in time from the timeof opening the fuel injection valve by a time interval corresponding tosaid output value; and (j) closing the fuel injection valve responsivelyto said displaced control signal.
 3. The method of claim 1, furthercomprising the step of producing a clock pulse signal independent of andof higher frequency than said crank angle pulse signal, and wherein saidstep of calculating basic fuel injection duration begins in response toeach pulse of the clock pulse signal.
 4. The method of claim 3, whereinthe step of calculating an output value begins immediately after eachstep of calculating the basic fuel injection duration, andfurthercomrising the step of storing the output value in an output interfaceprovided for the engine until updated by the next output value for usein the step of closing the fuel injection valve.
 5. The method of anyone of claims 1-4, further comprising the step of measuring intake airflow into the engine,wherein the basic fuel injection duration iscalculated on the basis of engine rotation speed as measured via theengine crankshaft, and intake air flow.
 6. The method of any one ofclaims 1-4, wherein said step of measuring a plurality of other engineoperating conditions further comprises the steps of:measuring enginecoolant temperature, and measuring exhaust gas oxygen concentration,wherein said step of calculating a fuel injection duration adjustment isbased on said measured engine temperature, exhaust gas oxygenconcentration, and engine load.
 7. The method of claim 6 wherein saidstep of measuring a plurality of other engine operating conditionsfurther comprises the step of measuring throttle valve angle.